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Genetic discovery links autism and schizophrenia

SCHIZOPHRENIA, autism and intellectual disability may all share a common genetic pathway.

Nelson Freimer at the University of California, Los Angeles, and colleagues studied an isolated community in Finland where schizophrenia and other neurological disorders are unusually common, possibly due to unavoidable inbreeding.

His team identified that 18 of 173 people from the community lacked a group of genes. Just one of 1586 samples from people throughout Finland were missing the same genes. Tests revealed that these deletions are more common in people with schizophrenia or cognitive impairments.

Further investigation showed that the deleted region normally contains a gene that makes an enzyme called topoisomerase III beta (TOP3B). A separate team also discovered that this enzyme regulates the winding and unwinding of RNA.

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In addition, the second team found that TOP3B has a role in the mechanisms that lead to fragile X syndrome. Like schizophrenia fragile X is thought to result from abnormal brain development.

Although the researchers do not yet know how disruptions in TOP3B affect brain development, they say the most likely explanation is that it changes the shape of the RNA, and thereby disturbs which RNA molecules get copied into proteins. This could cause neurons to grow and connect in a haphazard way – as is seen in several brain disorders (Nature Neuroscience, doi.org/ncq).